This invention relates generally to pneumatic rotary tools and more specifically to a pneumatic rotary tool having a reversible valve assembly for controlling the direction of airflow through the tool and the direction of rotational output of the tool.
Pneumatic rotary tools are commonly used in applications where it is desirable to turn a fastener element, such as a bolt or nut, in a forward or a reverse direction for tightening or loosening it. Pneumatic rotary tools are advantageous because they can rapidly rotate the fastener element for tightening or loosening the fastener element. Some pneumatic tools are capable of imparting large amounts of torque to the fastener. This is particularly desirable in automotive repair and industrial applications where fasteners may be difficult to loosen or may require large amounts of torque to tighten.
Pneumatic rotary tools typically include an output member (e.g., a socket) sized to engage the fastener. Pressurized air flows through the tool and drives an air motor which in turn drives the socket. Air typically flows to the motor through one of two passages. When air flows through a first passage, it drives the motor in a forward (generally tightening) direction. When air flows through a second passage, it drives the motor in a reverse (generally loosening) direction.
A valve is used to direct the air flow to the first or second passage. Typically, the valve includes a directional channel to direct the air to the desired passage and an arm connected to the valve for moving the directional channel to the desired position. In many tools, the arm extends laterally outward from the tool at a location, for example, above the trigger. Alternatively, a pair of arms may be used to move the valve. In U.S. Pat. No. 5,199,460 (Geiger), for example, air flows through a tubular spool to either a forward supply port or a reverse supply port. A rack and pinion system rotates the spool and aligns it with the desired port. Two arms (racks) are located on opposite sides of the spool (pinion) so that the desired arm may be pressed into the housing to rotate the spool to the desired position. When one arm is pressed into the housing, the opposite arm moves out of the housing in a rearward direction. The outward arm can subsequently be pressed into the housing to change the position of the spool.
A drawback to valves currently used is that the structure used to move the valves (e.g., the arm(s)) often protrudes outward from the tool, leaving it susceptible to inadvertent contact or movement during operation. It would therefore be desirable to provide a pneumatic tool with a simple valve construction that securely remains in the desired operating position under normal operation conditions.